A dialysis system is used as a substitute for the natural kidney functions of a human body. The dialysis system cleans the blood of the natural accumulation of bodily wastes by separating the wastes from the blood outside or extracorporeally of the body. The separated wastes are discharged and the cleansed blood is returned to the body.
The dialysis system consists of a dialysis machine, a dialyzer, a disposable blood tubing set and a supply of chemicals for producing a dialysate solution used within the dialyzer. The dialyzer is used with the dialysis machine to separate the wastes from the blood. The dialyzer includes a porous membrane located within a closed housing which effectively separates the housing into a blood compartment and a dialysate or filtrate compartment. The blood removed from the patient flows through the disposable blood tubing set and the blood side of the dialyzer. The dialysate solution prepared from the chemicals is passed through the dialysate side of the dialyzer. The wastes from the blood pass through the membrane by osmosis, ionic transfer or fluid transport into the dialysate and, depending upon the type of dialysis treatment, desirable components from the dialysate may pass in the opposite direction through the membrane and into the blood. The transfer of the wastes into the dialysate cleanses the blood while allowing the desired components from the dialysate to enter the bloodstream.
The transfer of blood between the patient and the dialyzer occurs within a disposable blood tubing set. The blood tubing set and the dialyzer represent a closed extracorporeal path through which the patient's blood travels. The blood tubing set includes an arterial line connected to an arterial reservoir for drawing blood from a patient, a venous line connected to a venous reservoir for returning blood to the patient, and a number of other lines for connecting a pump and the dialyzer between the arterial and venous reservoirs. Before the blood tubing set and the dialyzer can be used in a dialysis treatment, both must be primed with a sterile saline solution to remove air from the extracorporeal circuit. Once primed, the saline solution is recirculated through the blood tubing set and the dialyzer to produce a stabilized flow and remove additional trapped air from within the extracorporeal circuit. The priming and recirculating process also serves to clean the dialyzer and flush the dialyzer membrane of any debris or chemicals remaining from a prior use.
If a patient reuses the same dialyzer for subsequent dialysis treatments, that dialyzer must be cleaned with a disinfectant or sterilant solution. However, the sterilant itself must be cleaned from the dialyzer prior to each dialysis treatment. Such a cleaning procedure effectively takes place when the dialyzer undergoes the priming and recirculating process discussed above.
After completion of the prime and recirculation steps (i.e., when the blood tubing set is filled with saline), the arterial line of the blood tubing set is connected to the patient in the usual manner of dialysis systems. Blood is then drawn from the patient into the arterial line by a blood pump. The blood tends to replace the saline within the blood tubing set, and the saline is discarded down a waste drain until the blood tubing set is substantially filled with blood. The venous line is then connected to the patient to complete the extracorporeal circuit and allow the blood to travel through the arterial line, the dialyzer and back to the patient through the venous line.
At the conclusion of the dialysis treatment, but before the patient is completely disconnected from the dialysis machine, blood remaining in the blood tubing set must be returned to the patient. This is typically accomplished in one of two ways. One procedure requires clamping and disconnecting the arterial line from the patient and then attaching the arterial line to a saline source. The arterial clamp is then opened and the blood pump is started to draw saline into the arterial line and force the remaining blood through the arterial line, the dialyzer, and the venous line and back into the patient. When substantially all the blood has been returned to the patient, the venous line is clamped and the pump is stopped. The patient can then be disconnected from the dialysis machine.
Another procedure for returning the blood remaining within the blood tubing set to the patient entails using the same saline source that is used to prime the blood tubing set. The saline source is connected to the arterial reservoir of the blood tubing set and the saline is gravity fed into the arterial reservoir to force the blood in the arterial line back into the patient. Once the blood within the arterial line has been returned to the patient and the arterial reservoir has been filled with saline, the arterial line is clamped and the blood pump is activated to pump the saline through the dialyzer and the venous reservoir to force the remaining blood back into the patient through the venous line. Once substantially all the blood has been returned to the patient, the venous line is clamped and the patient is disconnected from the dialysis machine.
Although both procedures return substantially all the patient's blood, neither procedure returns 100% of the blood. Thus, the saline within the blood tubing set is contaminated with the patient's blood. The blood tubing set is thus usually discarded with the remaining contaminated saline left inside.
Due to the contaminated saline, the blood tubing set is necessarily classified as bio-hazardous medical waste which is relatively expensive to dispose of in comparison to normal refuse. Bio-hazardous medical waste cannot be discarded as normal trash, but rather must be sealed and removed by special contractors. Hospitals and dialysis clinics must typically pay a premium price for every pound of medical waste. Since the used blood tubing set is typically filled with contaminated saline, this "water weight" significantly increases the disposal cost of the blood tubing set.
Additionally, if the dialyzer is to be reused, it must be detached from the blood tubing set before the set is discarded. This is typically accomplished by clamping the blood tubing set at the inlet and the outlet of the dialyzer so that the dialyzer can be detached without spilling the contaminated saline remaining within the blood tubing set. The dialyzer can then be reprocessed after the blood tubing set is discarded, but the dialyzer must be handled carefully due to the contaminated saline remaining within the blood compartment of the dialyzer.
Some clinics have attempted to recycle the blood tubing set together with the reusable dialyzers. However, reprocessing the dialyzer entails connecting the dialyzer to a different machine which can flush sterilant through the dialyzer. Thus, recycling the blood tubing set with the dialyzer requires extending the functionality of the dialyzer flushing machine to also flush the contaminated saline from the blood tubing sets. Two potentially serious problems may be associated with this recycling method. First, the dialyzer flushing machine is not adapted to handle the blood tubing set and thus the time and effort required to clean the blood tubing set on the machine is typically not cost-effective in relation to the cost of a new disposable blood tubing set. Secondly, and potentially more serious, the operator is required to handle the contaminated blood tubing set in an environment which the manufacturers of the "disposable" blood tubing set did not intend, thereby exposing the operator to very serious health risks.
These and other considerations have contributed to the evolution of the present invention which is summarized below.